The present invention relates to a scroll compressor for refrigeration or air-conditioning.
A scroll compressor of the aforementioned type is in, for example, U.S. Pat. No. 4,462,772, with the scroll compressor contained in a sealed chamber, wherein the lower end portion of a driving shaft is disposed in an oil sump of the compressor and an oil flow passage is formed through the shaft with a radial eccentricity. In this arrangement, a lubricating oil is supplied to rotating portions of the compressor by means of a centrifugal force generated in accordance with the magnitude of the eccentricity of the oil flow passage.
A disadvantage of the above-described arrangement resides in the fact that the lift or head of oil supply can not be made sufficiently large because the head depends on the diameter of the shaft, and more specifically, to that of the rotor section of a motor. In particular, as the centrifugal force is under the influence of a rotational speed of the shaft, a sufficient oil supply head can not be obtained when the rotational speed of the compressor varies due to, for example, the driving by an inverter, particularly during its operation at a low rotational speed.
Although the oil supply pump provided at the end of the driving shaft may be increased in capacity in order to overcome the above disadvantage, such increase brings another disadvantage that the arrangement becomes complicated in structure and increased in size.